Notices by ✧✦✶✷Catherine✷✶✦✧ (whitequark@mastodon.social)

"we still don't know how to do JTAG"

but!
but!!!
i haven't shown you the best part yet
it's buried on page 1451 of a 1475 page datasheet

read every single footnote carefully

what they say (and partly, don't say) is: if you inject more than +2000, -500 microamps into most of its IO pads, the device gains an intenal short to ground

the only way to avoid this is resistors on basically every pin

this happened because the ESD structures were too expensive to buy from TSMC and the startup Luminary Micro designed their own

"don't write the internal EEPROM more than 7 times per word"

"if you toggle a GPIO too quickly you can overheat it"

by the way, this is errata GPIO#10. only four out of ten are public :)

don't worry about it :) :)

remember Stellaris MCUs with this amazing errata? i love it so much https://www.ti.com/lit/er/spmz861/spmz861.pdf?ts=1740672431462

it goes on by the way

you should read the full 52 page document, it's very entertaining

it goes on and on and on please read the full document

their estimated attrition rate over 10 years is *one percent of all MCUs shipped* even if you keep them powered on so they can ECC themselves

this is bonkers

it also has other errata, like "JTAG doesn't work" and "PWM doesn't work" and "timers don't work" and "ADCs don't work" and "we don't know how to do CDC" ... well you get the idea. read the full document!

"don't execute these particular accesses to SRAM, including if they are split across functions or interrupts. how? well uhhh... idk"

while the device is reset it configures pullups/pulldowns in a way that causes it to clock its own JTAG, and the workaround is to write some code that does this _on purpose_ to perform a TAP reset on every CPU reset

you can't make this up

"sometimes our core will execute random parts of your code during reset. knock yourself out"

no comment

"ROM bootloader cannot program a blank device"

"don't close a switch too fast or you'll kill the entire supply pin"

this one is from a related errata document

https://www.ti.com/lit/er/spmz849f/spmz849f.pdf (84 pages)

"watchdog cannot be cleared and resets the core even if not programmed to reset the core"

i like that the second message ever transmitted over the Moscow-Washington hotline was basically "Jesse what the fuck are you talking about"

@mcc @foone yeah i can do this in python, one sec

@mcc @foone easy